Question

A generalized expression of the r-value is ri calculated based on the following formula _______

(a) ri = ∑dij + dj^2

(b) ri = ∑dij

(c) ri = ∑dij + di

(d) ri = ∑dij + dj

I got this question in a job interview.

This interesting question is from Distance Based Methods topic in section Phylogenetic Tree Construction Methods and Programs of Bioinformatics

Answer 1

Right option is (b) ri = ∑dij

The explanation is: i and j are two different taxa. The r-values are needed to create a modified distance matrix. The transformed r-values (r ‘) are used to determine the distances of an individual taxon to the nearest node: r i^2 = ri/ (n−2).